ransac.h

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#ifndef TAG_RANSAC_H_
#define TAG_RANSAC_H_

#include <vector>
#include <algorithm>

namespace tag {


 template <class T> void randomTuple(const std::vector<T>& cdf, std::vector<unsigned int>& t, T maxp) {
     for (size_t i=0; i<t.size(); i++) {
     try_again:
     double x = drand48()* maxp;
     size_t r = std::min(cdf.size()-1, (size_t)(std::lower_bound(cdf.begin(), cdf.end(), (T)x) - cdf.begin()));
     for (size_t j=0; j<i; j++)
         if (r == t[j])
         goto try_again;
     t[i] = r;
     }
 }

 template <class T> void randomTuple(T& t, unsigned int bound)
 {
     for (size_t i=0; i<t.size(); i++) {
     try_again:
     size_t r = (size_t)(drand48() * bound);
     for (size_t j=0; j<i; j++)
         if (r == t[j])
         goto try_again;
     t[i] = r;
     }
 }



template <class Obs, class Trans, class Tol> size_t find_RANSAC_inliers(const std::vector<Obs>& observations, int sample_size, const Tol& tolerance, size_t N,
                                    Trans& best, std::vector<bool>& inlier)
{
    std::vector<bool> thisInlier(observations.size());
    size_t bestScore = 0;
    std::vector<size_t> sample_index(sample_size);
    std::vector<Obs> sample(sample_size);
    while (N--) {
    randomTuple(sample_index, observations.size());
    for (int i=0;i<sample_size; i++)
        sample[i] = observations[sample_index[i]];
    Trans thisT(best);
    thisT.estimate(sample.begin(), sample.end());
    size_t score = 0;
    for (size_t i=0; i<observations.size(); i++) {
        const Obs& o = observations[i];
        if (thisT.isInlier(o, tolerance)) {
        thisInlier[i] = true;
        score++;
        } else
        thisInlier[i] = false;
    }
    if (score > bestScore) {
        bestScore = score;
        inlier = thisInlier;
        best = thisT;
    }
    }
    return bestScore;
}

template <class Obs, class Trans, class Tol> double find_MSAC_inliers(const std::vector<Obs>& observations, int sample_size, const Tol& tolerance, size_t N,
                                    Trans& best, std::vector<bool>& inlier)
{
    std::vector<bool> thisInlier(observations.size());
    const double toleranceSquared = tolerance * tolerance;
    double bestScore = observations.size() * toleranceSquared;

    std::vector<size_t> sample_index(sample_size);
    std::vector<Obs> sample(sample_size);
    while (N--) {
    randomTuple(sample_index, observations.size());
    for (int i=0;i<sample_size; i++)
        sample[i] = observations[sample_index[i]];
    Trans thisT(best);
    thisT.estimate(sample.begin(), sample.end());
    double score = 0;
    for (size_t i=0; i<observations.size(); i++) {
        const Obs& o = observations[i];
        const double s = thisT.score(o);
        if (s < toleranceSquared) {
        thisInlier[i] = true;
        score += s;
        } else {
        thisInlier[i] = false;
        score += toleranceSquared;
        }
    }
    if (score < bestScore) {
        bestScore = score;
        inlier = thisInlier;
        best = thisT;
    }
    }
    return bestScore;
}

 inline double getShrinkRatio(unsigned int H, unsigned int N, unsigned int B)
 {
     return pow(double(H), -double(B)/N);
 }



     template <class Obs, class Trans, class Tol, class Prob>
    size_t find_RANSAC_inliers_guided_breadth_first(const std::vector<Obs>& observations, const Prob& prob, int sample_size, const Tol& tolerance, size_t N, size_t block_size,
                            Trans& best, std::vector<bool>& inlier)
    {
    std::vector<Trans> hypotheses(N,best);
    std::vector<std::pair<int,size_t> > score(N);
    std::vector<size_t> sample_index(sample_size);
    std::vector<Obs> sample(sample_size);
    std::vector<double> cdf(observations.size());
    cdf[0] = prob(observations[0]);
    for (size_t i=1; i<observations.size(); ++i)
        cdf[i] = cdf[i-1] + prob(observations[i]);
    const double psum = cdf.back();

    for (size_t i=0; i<hypotheses.size(); i++) {
        do {
        randomTuple(cdf, sample_index, psum);
        for (int s=0; s<sample_size; ++s)
            sample[s] = observations[sample_index[s]];
        }
        while (!hypotheses[i].estimate(sample.begin(), sample.end()));
        score[i] = std::make_pair(0,i);
    }
    size_t m = 0;
    const double factor = getShrinkRatio(N, observations.size(), block_size);
    while (m < observations.size()) {
        size_t end = std::min(observations.size(), m+block_size);
        for (size_t i=0; i<score.size(); i++) {
        const Trans& thisT = hypotheses[score[i].second];
        size_t s = 0;
        for (size_t j=m; j!=end; j++) {
            if (thisT.isInlier(observations[j], tolerance))
            ++s;
        }
        score[i].first += s;
        }
        unsigned int cutoff = (unsigned int)(score.size() * factor);
        if (cutoff == 0)
        break;
        std::nth_element(score.begin(), score.end(), score.begin()+cutoff, std::greater<std::pair<int,size_t> >());
        score.resize(cutoff);
        m = end;
    }
    size_t best_index = std::max_element(score.begin(), score.end())->second;
    best = hypotheses[best_index];
    size_t count = 0;
    inlier.resize(observations.size());
    for (size_t i=0; i<observations.size(); i++) {
        if (best.isInlier(observations[i], tolerance)) {
        inlier[i] = true;
        ++count;
        } else
        inlier[i] = false;
    }
    return count;
    }



    template <class Obs, class Trans, class Tol> size_t find_RANSAC_inliers_breadth_first(const std::vector<Obs>& observations, int sample_size, const Tol& tolerance, size_t N, size_t block_size,
                                              Trans& best, std::vector<bool>& inlier)
    {
    std::vector<Trans> hypotheses(N,best);
    std::vector<std::pair<int,size_t> > score(N);
    std::vector<size_t> sample_index(sample_size);
    std::vector<Obs> sample(sample_size);
    for (size_t i=0; i<hypotheses.size(); i++) {
        do {
        randomTuple(sample_index, observations.size());
        for (int s=0; s<sample_size; ++s)
            sample[s] = observations[sample_index[s]];
        }
        while (!hypotheses[i].estimate(sample.begin(), sample.end()));
        score[i] = std::make_pair(0,i);
    }
    size_t m = 0;
    const double factor = getShrinkRatio(N, observations.size(), block_size);
    while (m < observations.size()) {
        size_t end = std::min(observations.size(), m+block_size);
        for (size_t i=0; i<score.size(); i++) {
        const Trans& thisT = hypotheses[score[i].second];
        size_t s = 0;
        for (size_t j=m; j!=end; j++) {
            if (thisT.isInlier(observations[j], tolerance))
            ++s;
        }
        score[i].first += s;
        }
        unsigned int cutoff = (unsigned int)(score.size() * factor);
        if (cutoff == 0)
        break;
        std::nth_element(score.begin(), score.end(), score.begin()+cutoff, std::greater<std::pair<int,size_t> >());
        score.resize(cutoff);
        m = end;
    }
    size_t best_index = std::max_element(score.begin(), score.end())->second;
    best = hypotheses[best_index];
    size_t count = 0;
    inlier.resize(observations.size());
    for (size_t i=0; i<observations.size(); i++) {
        if (best.isInlier(observations[i], tolerance)) {
        inlier[i] = true;
        ++count;
        } else
        inlier[i] = false;
    }
    return count;
    }


template <class T, class U>
void remove_if_false(std::vector<T>& v, const std::vector<U>& flag) {
    assert(v.size() <= flag.size());
    unsigned int i=0,j;
    while (i<v.size() && flag[i])
        i++;
    j = i++;
    for (;i<v.size();i++) {
        if (flag[i])
            v[j++] = v[i];
    }
    v.resize(j);
}

} // namespace tag

#endif

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